A small-size electronic device having a memory function, such as a pocket-size computers needs a main battery for operating the device, and a memory backup battery for retaining data in a memory when a supply of power is suspended, for example, during replacement of the main battery.
In such an electronic device, if a user mistakenly removes the memory backup battery from the device together with the main battery when replacing the main battery, data stored in a memory such as SRAM (Static Random Access Memory) is lost. To prevent such a trouble, the electronic device needs to have a battery storage mechanism which allows replacing the memory backup battery only when the main battery is stored, and allows replacing the main battery only when the memory backup battery is stored.
For example, a pocket-size computer (model number: PA-X1) produced by Sharp has such a battery storage mechanism. The mechanism is explained below with reference to FIGS. 7 and 8.
This battery storage mechanism has holders 23 and 24 which have a circular cross-section and hold two disk-shaped batteries 21 and 22 when inserted therein. The holders 23 and 24 are disposed adjacent to each other on a chassis 25. The batteries 21 and 22 are held in the holders 23 and 24 by pushing them toward the center of the holders 23 and 24 with pushing means such as a flat spring, not shown.
The chassis 25 has cuts 23a and 24a for assisting the removal of the batteries 21 and 22 from the holders 23 and 24. The cuts 23a and 24a are made on a tangent line touching edges of the holders 23 and 24.
In order to prevent the removal of the battery 21 from the holder 23, a first battery lid 26 is mounted to be movable in a diametrical direction of the holder 23. More specifically, the first battery lid 26 is movable between a removal protect position and a removal permit position. In the removal protect position, part of the holder 23 and the entire cut 23a are covered with the battery lid 26. In the removal permit position, the cut 23a is not covered with the battery lid 26 so that a stick-like jig is inserted into the cut 23a to remove the battery 21 from the holder 23.
In order to prevent the removal of the battery 22 from the holder 24, a second battery lid 27 having a structure similar to that of the first battery lid 26 is mounted to be movable in a diametrical direction of the holder 24.
Since these battery lids 26 and 27 are provided for covering the cuts 23a and 24a, they do not have a function to hold the batteries 21 and 22. In other words, whilst the battery lids 26 and 27 cover part of the batteries 21 and 22 stored in the holder 23 and 24, they are not in contact with the batteries 21 and 22.
A near rectangular switch plate 28 for restricting movements of the first battery lid 26 and second lid 27 is mounted to be movable on the above-mentioned tangent line against the chassis 25. Disposed at the center of the switch plate 28 is a knob 28a which is to be held by the hand when moving the switch plate 28.
The switch plate 28 has a first raised section 28b for preventing a movement of the first lid 26, and a second raised section 28c for preventing a movement of the second lid 27. When the knob 28a is in a position substantially aligned with a first mark 29a indicating the removal protect position (standby position), edges of the first lid 26 and second lid 27 come into contact with the first raised section 28b and second raised section 28c, respectively, to prevent the movements of the first lid 26 and second lid 27.
When the knob 28a is moved to a position substantially aligned with a second mark 29b indicating a position where a removal of the battery 21 is available, the first raised section 28b comes to a position where it is unable to prevent a movement of the first lid 26 and the second raised section 28c comes to a position where it is able to prevent a movement of the second lid 27.
When the knob 28a is moved to a position substantially aligned with a third mark 29c indicating a position where a removal of the battery 22 is available, the second raised section 28c comes to a position where it is unable to prevent a movement of the second lid 27 and the first raised section 28b come to a position where it is able to prevent a movement of the first lid 26.
Mounted on a back surface of the chassis 25 is a substantially U-shaped first rib 30 which controls a movement of the switch plate 28 by detecting whether the battery 21 is stored in the holder 23. As illustrated in FIG. 8, the first rib 30 is pushed toward the front surface of the chassis 25 by a coil spring 30a.
The chassis 25 has a through-hole 25a. A detection end 30b as one of the ends of the first rib 30 passes through-hole 25a and is inserted into the holder 23 from the back surface of the chassis 25.
The chassis 25 also has a through-hole 25b. A lock end 30c as the other end of the first rib 30 passes through the through-hole 25b and comes into contact with the back surface of the switch plate 28.
Moreover, a substantially U-shaped second rib 31 is mounted on the back surface of the chassis 25 like the first rib 30. The second rib 31 controls a movement of the switch plate 28 by detecting whether the battery 22 is stored in the holder 24.
A first lock hole 32 is formed in the back surface of the switch plate 28 so that the lock end 30c of the first rib 30 fits into the first lock hole 32 when the switch plate 28 is moved to a position where the knob 28a is in a position substantially aligned with the second mark 29b.
When the battery 21 is removed form the holder 23 after moving the switch plate 28 to the position where the knob 28a is in the position substantially aligned with the second mark 29b, the first rib 30 which has been pushed down by the battery 21 is moved toward the front surface of the chassis 25 by the coil spring 30a. Therefore, the lock end 30c fits into the first lock hole 32 and prevents a movement of the switch plate 28.
Furthermore, a second lock hole 33 is formed in the back surface of the switch plate 28 so that the lock end 31c of the second rib 31 fits into the second lock hole 33 when the switch plate 28 is moved to a position where the knob 28a is substantially aligned with the third mark 29c. At this time, when the battery 22 is removed from the holder 24, the lock end 31c fits into the second lock hole 33 and prevents a movement of the switch plate 28.
The following description discusses an operation of the battery storage mechanism. When the electronic device is operated normally, the cuts 23a and 24a are covered with the first lid 26 and second led 27. Therefore, the removal of the first and second batteries 26 and 27 becomes unavailable.
At this time, the knob 28a of the switch plate 28 is substantially aligned with the first mark 29a, and the first raised section 28b and second raised section 28c of the switch plate 28 are in the position to prevent the movements of the first lid 26 and second lid 27.
Next, for example, replacing the battery 21 is discussed below. As illustrated in FIGS. 9 and 10, when the knob 28a is moved to the position where it is substantially aligned with the second mark 29b, i.e., replacement position of the battery 21, the first raised section 28b of the switch plate 28 comes to the position where it is unable to prevent a movement of the first lid 26. At this time, the second raised section 28c of the switch plate 28 comes to a position where it is able to prevent a movement of the second lid 27.
After opening the first lid 26 to expose the cut 23a, for example, a stick-like jig is inserted into the cut 23a to remove the battery 21 from the holder 23. Then, the detection end 30b of the first rib 30 comes out of contact with the battery 21, and the first rib 30 is moved toward the front surface of the chassis 25 by the coil spring 30a.
As a result, the lock end 30c fits into the first lock hole 32 and prevents a movement of the switch plate 28. When a new battery 21 is stored in the holder 23, the detection end 30b is pushed by the battery 21 and the first rib 30 is moved toward the back surface of the chassis 25 against the pushing force of the coil spring 30a. Consequently, the lock end 30c and the first lock hole 32 come out of contact with each other.
Finally, the first lid 26 is moved to cover the cut 23a and the switch plate 28 is moved back to the initial position to complete the replacement of the battery 21. The battery 22 is also replaced in the same manner.
With this structure, however, replacing the battery 21 for example requires a complicated process, i.e., three steps of actions: moving the switch plate 28 to the replacement position; moving the first lid 26; and removing the battery 21. In addition, since the mechanism is complicated, the manufacturing cost is increased and the rate of defective products is hard to be decreased.